Many ophthalmologic surgical procedures require the use of a microscope for the performance thereof. A conventional ophthalmologic microscope has one or more objective lenses (depending on whether it is a binocular microscope) and an illumination source. It is also well known in the art to include a gaze-fixing device with the microscope to keep the patients focus in one particular position while the surgery is performed. Often the gaze-fixing device uses the same light as the illumination source. Sometimes, the gaze-fixing light is directed through the object lens of the microscope.
It is also known to include a gaze-fixing device consisting of a light emitting diode (LED) located between the objective lens and the patient's eye, but within the light ray path of the object lens, such as that taught by Takagi et al. in U.S. Pat. No. 4,793,700. Takagi teaches a red LED focus light as a gaze-fixing device located in an optical axis of the microscope, which is particularly important in radial keratotomy (RK) surgery. The illumination source in Takagi is of the conventional type, whereby the light passes through the one of the object lenses, albeit a few degrees off of the optical axis.
Another problem with ophthalmologic microscopes is that the intense illumination source over the course of a surgical procedure, such as a cataract removal, can cause photophobia and/or phototoxicity, possibly causing a burn on the retina. This is especially true when the eye of the patient is focused in the same general direction as the illumination source, as is the case with conventional microscopes. The light from the illumination source hits the retina on the macula, which is particularly light sensitive and probably the most important part of the retina for vision.
It is known to reroute a significant portion of the illumination source so that it hits the patient's eye at an angle. This causes much of the high intensity light to hit the retina in less photosensitive areas than the macula. Such a solution is disclosed in U.S. Pat. No. 5,155,509 to Kleinberg. Such solutions are not ideal, however, because it is preferable for many types of surgery to retain a majority of the illumination source close to the visual axis of the microscope, as is the case with conventional microscopes. These solutions also lack a gaze-fixing device to keep the patient's eye from moving. Furthermore, these solutions require a complex array of mirrors and want for simplification.
Takagi purports to reduce excessive stimulus of light on the macula with the gaze-fixing device. Although such exposure may be reduced somewhat, the illumination source is still directed through the object lens, and thus not sufficiently off-angle from the optic axis to hit the insensitive optic nerve.
Thus, it is an object of the present invention to provide a gaze-fixing device for an ophthalmologic microscope that keeps the patient's focus approximately 18.degree.-20.degree. offset from the illumination source.
It is a further object of the present invention to provide such a gaze-fixing device that can be attached to a conventional ophthalmologic microscope.
It is yet a further object of the present invention to provide a secondary gaze-fixing device to aid the ophthalmologist in making incisions on other parts of the eye.